* The summer solstice is the longest day of the year. In Chicago, we will see 15 hours and 13 minutes of daylight. Starting June 22, the days get shorter.

* The word “solstice” comes from the Latin words for “sun” and “to stand still.”  The noontime elevation of the sun does not visibly change from day to day around the time of the solstice, making it seem like the sun is standing still.

* On the solstice, the sun reaches its most northern point in the Northern Hempisphere. The sun is at a zenith, directly above the Tropic of Cancer, which is 23.5 degrees north latitude.

* Even though the sun is at its highest point in the sky, nowhere in the 48 continental United States can the sun appear directly overhead. (That’s because the Tropic of Cancer is south of the U.S. mainland)

* It is only summer in the Northern Hemisphere. In the Southern Hemisphere, it is winter.

* The longest day of the year is not the hottest day of the year. The time it takes time for the energy absorbed by the atmosphere and oceans to re-radiate across the land is known as the “seasonal temperature lag.” Short answer: the Earth, like an oven, takes time to warm up.

* A common misconception is that the Earth is closest to the sun on the summer solstice. That isn’t true. It’s all about the tilt of the Earth toward the sun, and the North Pole the tilted toward the sun on the solstice than any other day of the year.

* Stonehenge was constructed 4,000 years ago as a temple to the sun. The group English Heritage has done recent excavations at the site, discovering that it was built on the solstice axis. The group believes that Stonehenge was built as a temple and purposefully aligned with the movements of the sun. It still draws large crowds on the summer solstice.

* Between 2015 and 2020, the summer solstice will fall on June 21st with the exception of 2016, when it will be June 20th.

Sources: NASA SciJinks; TimeandDate.com for Chicago; Huffington Post; “Stonehenge was built on solstice axis, dig confirms” The Guardian, Sept. 18, 2013; The International Business Times; the U.S. Naval Observatory.

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